Which combination of findings on an ECG is characteristic of Wolff-Parkinson-White pattern?

• A. Short PR interval, delta wave, wide QRS
• B. Prolonged PR interval, delta wave, narrow QRS
• C. Normal PR interval, delta wave, narrow QRS
• D. Short PR interval, no delta wave, narrow QRS

Answer: (A)

Wolff-Parkinson-White pattern comes from an accessory pathway that bypasses the AV node and pre-excites the ventricles. This early ventricular activation shortens the PR interval because the impulse reaches the ventricles faster than through the AV node. The pre-excitation creates a delta wave, a slurred upstroke at the start of the QRS, showing the ventricle is starting to depolarize via the abnormal pathway. Because part of the ventricle is activated early through the accessory pathway and the rest through the normal conduction system, the overall QRS becomes wider than normal. So the classic WPW pattern is a short PR interval, a delta wave, and a wide QRS.

If any of these features are missing—for example a normal PR interval, or no delta wave, or a narrow QRS—the finding does not fit WPW.